Adjust the source code and build enviornment so that Mangos Zero will…

… build on ARM32. (mangoszero#79)

This was primarily done to test the feasibility of running on a RPi4 running
Debian Buster (it works quite well).

Summary of changes:

  - Reworked patches I found on the Mangos forum, original pastebins here:
      https://pastebin.com/BxqCmCML
  - Adjusted cmake's arch detection to include ARM32/ARM64
  - Adjusted compiler flags for Linux builds and supressed some extraneous notes

I have played for about an hour and noticed no issues or differences from i386/x86_64 VMs.

One note, currently the map extraction tools for ARM are broken.  They compile but do
work properly.  I'll work on that next.

cmake/SetDefinitions.cmake

@@ -23,14 +23,21 @@ else()
 endif()
 
 if(XCODE)
-  if(PLATFORM MATCHES 32)
+  # Here we add a check for ARM32, as they can't leverage SSE/SSE2
+  if(PLATFORM MATCHES 32 AND ${CMAKE_SYSTEM_PROCESSOR} MATCHES "^arm")
+    set(CMAKE_OSX_ARCHITECTURES ARM32)
+  # Default for 32-bit left as i386
+  elseif(PLATFORM MATCHES 32)
     set(CMAKE_OSX_ARCHITECTURES i386)
+  # Check for ARM64
+  elseif(PLATFORM MATCHES 64 AND ${CMAKE_SYSTEM_PROCESSOR} MATCHES "^arm") 
+    set(CMAKE_OSX_ARCHITECTURES ARM64)
+  # Default for 64-bit left as x86_64
   else()
     set(CMAKE_OSX_ARCHITECTURES x86_64)
   endif()
 endif()
 
-
 #
 # Compile definitions
 #
@@ -112,10 +119,17 @@ endif ()
 # GCC compiler options
 if ("${CMAKE_CXX_COMPILER_ID}" MATCHES "GNU")
     set(DEFAULT_COMPILE_OPTS ${DEFAULT_COMPILE_OPTS}
-        $<$<EQUAL:${PLATFORM},32>:
+	# Enhanced 32-bit check, now we can use the arch to specify flags
+	$<$<STREQUAL:${CMAKE_OSX_ARCHITECTURES},"i386">:
             -msse2
             -mfpmath=sse
         >
+	$<$<STREQUAL:${CMAKE_OSX_ARCHITECTURES},"ARM32">:
+	# explicit space for compiler flags
+	>
+        $<$<STREQUAL:${CMAKE_OSX_ARCHITECTURES},"ARM64">:
+        # explicit space for compiler flags
+        >
         $<$<CONFIG:Debug>:
           -W
           -Wall
@@ -128,6 +142,9 @@ if ("${CMAKE_CXX_COMPILER_ID}" MATCHES "GNU")
 
         $<$<CONFIG:Release>:
           --no-warnings
+	  # Suppress compiler note on parameter passing.  See the following
+	  # GCC BZ for more info:  https://gcc.gnu.org/bugzilla/show_bug.cgi?id=77728
+	  -Wno-psabi
         >
     )
 endif ()

src/shared/Database/SQLStorageImpl.h

@@ -40,6 +40,14 @@ template<class S, class D>
  */
 void SQLStorageLoaderBase<DerivedLoader, StorageClass>::convert(uint32 /*field_pos*/, S src, D& dst)
 {
+#if defined(__arm__)
+    if (((unsigned) &dst) % sizeof(D)) {
+        //The address is not aligned. Use memcpy to avoid ARM unaligned trap
+       D converted(src);
+       memcpy((void*) &dst, (void*) &converted, sizeof(D));
+    }
+    else
+#endif
     dst = D(src);
 }
 
@@ -92,6 +100,14 @@ template<class D>
  */
 void SQLStorageLoaderBase<DerivedLoader, StorageClass>::convert_from_str(uint32 /*field_pos*/, char const* /*src*/, D& dst)
 {
+#if defined(__arm__)
+    if (((unsigned) &dst) % sizeof(D)) {
+       //The address is not aligned. Use memcpy to avoid ARM unaligned trap
+       D converted(0);
+       memcpy((void*) &dst, (void*) &converted, sizeof(D));
+    }
+    else
+#endif
     dst = 0;
 }
 
@@ -106,6 +122,14 @@ template<class S, class D>
  */
 void SQLStorageLoaderBase<DerivedLoader, StorageClass>::default_fill(uint32 /*field_pos*/, S src, D& dst)
 {
+#if defined(__arm__)
+    if (((unsigned) &dst) % sizeof(D)) {
+       //The address is not aligned. Use memcpy to avoid ARM unaligned trap
+       D converted(src);
+       memcpy((void*) &dst, (void*) &converted, sizeof(D));
+    }
+    else
+#endif
     dst = D(src);
 }
 

src/shared/Utilities/ByteBuffer.h

@@ -534,7 +534,13 @@ class ByteBuffer
         {
             if (pos + sizeof(T) > size())
                 { throw ByteBufferException(false, pos, sizeof(T), size()); }
+#if defined(__arm__)
+            // ARM has alignment issues, we need to use memcpy to avoid them
+            T val;
+            memcpy((void*)&val, (void*)&_storage[pos], sizeof(T));
+#else
             T val = *((T const*)&_storage[pos]);
+#endif
             EndianConvert(val);
             return val;
         }